Great atmosphere and visuals! I couldnt get the first puzzle on my first try (as in i found the number but didnt know what to do with it!) so had to look up a few comments. But then got it unlocked. The horror elements are definitely there and I had a couple of jumpscares. Adding some very subtle background score would go a long way in adding to the creepy vibe i think.
Overall it has the foundations for a really good horror game and you have nailed the artstyle, well done :)